1. Field of the Invention
The present invention generally relates to processing tools, methods of producing processing tools, processing methods and processing apparatuses, and more particularly to a processing tool which is used to grind a work-piece made of silicon or the like, a method of producing such a processing tool, a processing method for processing a peripheral part of a work-piece, and a processing apparatus
2. Discussion of Background
Conventionally, in a finishing process of a silicon wafer, a polishing process uses colloidal silica as the slurry and a flexible polishing cloth as the polishing tool. However, since the polishing process uses the slurry, there are problems in that the processing environment is harsh, the waste water must be processed, the running cost of the processing system is high, the processing efficiency is low, and the shaping accuracy (flatness) is poor. For this reason, there are demands to carry out the finishing process of the silicon wafer by a fixed-abrasive machining apparatus, that is, by use of a fixed-abrasive grinding tool such as a grindstone and a polishing film, and various tools therefor have been proposed.
As conventional techniques which utilize the mechano-chemical reaction between barium carbonate and silicon, there is a first conventional technique proposed in a Japanese Laid-Open Patent Application 5-285844, a second conventional technique proposed in a Japanese Laid-Open Patent Application No.5-285847, and a third conventional technique proposed in a Japanese Laid-Open Patent Application No.10-329032.
According to the first through third conventional techniques, the grindstone is formed by abrasive grains which are made of barium carbonate. By utilizing the mechano-chemical reaction that occurs between the abrasive grains and silicon, a processed surface having a high quality is obtained, similarly to a case where a loose-abrasive polishing process is carried out, such that no residual damage remains after the processing. In other words, it is possible, by using the barium carbonate for the abrasive grains, to replace the conventional polishing process by the grinding process.
On the other hand, silica generates a mechano-chemical reaction with respect to silicon. In addition, since the constituent elements of silica are silicon and oxygen, silica will not form on the silicon a residual contamination resulting from the mechano-chemical reaction between the silica and the silicon. Furthermore, since the mechanical hardness of silica is higher than that of barium carbonate, it is possible to realize a high removing efficiency while maintaining the high accuracy of the processed surface.
For example, in a fourth conventional technique proposed in a Japanese Laid-Open Patent Application No.8-276366, a resin bonded grindstone is produced by using silica as the aggregate. In fifth, sixth and seventh conventional techniques respectively proposed in Japanese Laid-Open Patent Applications No.5-285843, No.10-166259 and No.9-47969, the grindstone for grinding a sapphire substrate uses silica for the abrasive grains.
According to the fourth conventional technique, silica is not used for the abrasive grains, but is used for the aggregate, so as to improve the dispersibiity of the abrasive grains and improve the adjustment of the specific gravity of the binder.
According to the fifth and sixth conventional techniques, the grindstone for grinding sapphire is formed by using silica which is mechanically softer than sapphire. A high-quality grinding of sapphire is realized by utilizing the mechano-chemical reaction at a point of contact between the abrasive grains and the sapphire.
According to the seventh conventional technique, ultra-fine silica or silicon oxide powder having a grain diameter of several tens of nm or less is used as the abrasive grains. A silicon wafer or the like is mirror finished with a high accuracy without loading, by use of the grindstone which is formed at a predetermined porosity. It is, however, not the main object of the seventh conventional technique to generate the mechano-chemical reaction by the use of the silica abrasive grains.
When barium carbonate is used for the abrasive grains as in the case of the first through third conventional techniques, the mechano-chemical reaction between the barium carbonate and the silicon causes a compound thereof to be generated on the silicon as residual contamination. The compound is made up of barium, silicon and oxygen. Hence, the generated contamination deteriorates the quality of the processed surface, and it is necessary to carry out a cleaning process as an after-process. Moreover, the barium carbonate has a mechanical hardness lower than that of the silicon and is easier to process the barium carbonate with a high accuracy, but as a consequence, the removing efficiency is too low for use during the production process.
On the other hand, as in the case of the fourth conventional technique, silica is generally used as the aggregate, so as to improve the dispersibiity of the abrasive grains and improve the adjustment of the specific gravity of the binder, when carrying out the process using the resin bonded grindstone. In the fifth and sixth conventional techniques, silica is used as the abrasive grains for polishing sapphire, but no consideration is given on the use of silica as the abrasive grains for polishing a silicon wafer. Further, since the seventh conventional technique uses the silica powder having a grain diameter of several tens of nm or less, it is difficult to realize a high removing efficiency.
Accordingly, it is a general object of the present invention to provide a novel and useful processing tool, method of producing processing tool, processing method and processing apparatus, in which the problems described above are eliminated.
Another and more specific object of the present invention is to provide a processing tool, method of producing processing tool, processing method and processing apparatus, which use silica abrasive grains to generate a mechano-chemical reaction with respect to silicon but prevents residual contamination from remaining on the silicon due to the mechano-chemical reaction.
Still another object of the present invention is to provide a processing tool for carrying out a fixed-abrasive grinding process on a surface of a silicon work-piece, comprising abrasive grains made up silica grains. According to the processing tool of the present invention, it is possible to utilize the mechano-chemical reaction generated by the silica grains on the silicon work-piece, and realize a high removing efficiency while maintaining a high quality of the processed surface.
A further object of the present invention is to provide a method of producing a processing tool having abrasive grains for carrying out a fixed-abrasive grinding process on a surface of a silicon work-piece, comprising the step of (a) mixing a binder and silica grains to form a mixture, and (b) forming the mixture into the abrasive grains of the processing tool. According to the method of the present invention, it is possible to produce a processing tool which utilizes the mechano-chemical reaction generated by the silica grains on the silicon work-piece, to realize a high removing efficiency while maintaining a high quality of the processed surface.
Another object of the present invention is to provide a processing method for carrying out a fixed-abrasive grinding process on a surface of a silicon work-piece, comprising the steps of (a) positioning the silicon work-piece relative to a processing tool having abrasive grains made up silica grains, and (b) processing the surface of the silicon work-piece by the abrasive grains of the processing tool. According to the processing method of the present invention, it is possible to utilize the mechano-chemical reaction generated by the silica grains on the silicon work-piece, to realize a high removing efficiency while maintaining a high quality of the processed surface.
Still another object of the present invention is to provide a processing method for carrying out a process on a disk-shaped or donut-shaped work-piece, comprising the steps of (a) grinding an outer peripheral surface of the work-piece by a grindstone, and (b) polishing cutout part on the outer peripheral surface of the work-piece and/or an inner peripheral surface of the work-piece by a polishing film. According to the processing method of the present invention, it is possible to stably and suitably process various kinds of surfaces of the work piece with a high efficiency, so as to obtain processed surfaces having a high quality, at a low running cost.
A further object of the present invention is to provide a processing apparatus for carrying out a process on a disk-shaped or donut-shaped work-piece, comprising a grinding unit grinding an outer peripheral surface of the work-piece by a grindstone, a polishing unit polishing cutout part on the outer peripheral surface of the work-piece and/or an inner peripheral surface of the work-piece by a polishing film, and a transport unit transporting the work-piece at least between the grinding unit and the polishing unit and positioning the work-piece in the grinding unit and the polishing unit. According to the processing apparatus of the present invention, it is possible to stably and suitably process various kinds of surfaces of the work piece with a high efficiency, so as to obtain processed surfaces having a high quality, at a low running cost.